Even though I'm in market for MBP, I think the MB information is rather interesting. There have long been speculations that apple will go all aluminum through its portable products, and it seems very likely that an update like that would be worthy the developers conference in the summer.
The date of September seems also very likely, because it is the time when schools/universities usually start and that is an important market for macbook.
One thing that makes me a bit worried is the piece about one of MBs to be almost like a 13 inch MPB. The one thing that would bring the MB closer to MBP is dedicated graphics card, but I just don't see that happening. If there is gonna be a product that would basically be 13 inch MBP and it will be a MBP not a MB.
Penryn needs to come soon, my creditcard is begging me to be used.